add TemplateRule initialisation

Author: Mr-Leshiy

rust/signed_doc/src/validator/rules/mod.rs

@@ -127,7 +127,7 @@ impl Rules {
                 ver: VerRule,
                 content_type: ContentTypeRule::new(&doc_spec.headers.content_type)?,
                 content_encoding: ContentEncodingRule::new(&doc_spec.headers.content_encoding)?,
-                template: TemplateRule::NotSpecified,
+                template: TemplateRule::new(&spec.docs, &doc_spec.metadata.template)?,
                 parameters: ParametersRule::NotSpecified,
                 doc_ref: RefRule::new(&spec.docs, &doc_spec.metadata.doc_ref)?,
                 reply: ReplyRule::NotSpecified,

rust/signed_doc/src/validator/rules/template.rs

@@ -1,5 +1,11 @@
 //! `template` rule type impl.
 
+use std::collections::HashMap;
+
+use catalyst_signed_doc_spec::{
+    is_required::IsRequired, metadata::template::Template, DocSpec, DocumentName,
+};
+
 use crate::{
     providers::CatalystSignedDocumentProvider,
     validator::{
@@ -22,6 +28,39 @@ pub(crate) enum TemplateRule {
 }
 
 impl TemplateRule {
+    /// Generating `TemplateRule` from specs
+    pub(crate) fn new(
+        docs: &HashMap<DocumentName, DocSpec>,
+        spec: &Template,
+    ) -> anyhow::Result<Self> {
+        if let IsRequired::Excluded = spec.required {
+            anyhow::ensure!(
+            spec.doc_type.is_none() && spec.multiple.is_none(),
+            "'type' and 'multiple' fields could not been specified when 'required' is 'excluded' for 'template'  metadata definition"
+        );
+            return Ok(Self::NotSpecified);
+        }
+
+        anyhow::ensure!(
+            spec.multiple.is_some_and(|v| !v),
+            "'multiple' must be `false` for 'template' metadata definition"
+        );
+        anyhow::ensure!(
+            spec.required != IsRequired::Optional,
+            "'required' field cannot been 'optional' for 'template'  metadata definition"
+        );
+
+        let doc_name = spec.doc_type.as_ref().ok_or(anyhow::anyhow!(
+            "'type' field should exists for the required 'template' metadata definition"
+        ))?;
+        let docs_spec = docs.get(doc_name).ok_or(anyhow::anyhow!(
+            "cannot find a document definition {doc_name}"
+        ))?;
+        let allowed_type = docs_spec.doc_type.as_str().parse()?;
+
+        Ok(Self::Specified { allowed_type })
+    }
+
     /// Field validation rule
     pub(crate) async fn check<Provider>(
         &self,